With discharged batteries and a heavy load 13.2 volts may be all you get at
idle! What do you get above idle? If you can get 13.8 volts at the
alternator even if you have to rev the engine the alternator is doing its
job. It takes about 1800 to 2000 engine rpm for the alternator to reach full
output. With charged batteries and little load you will see the full voltage
at idle but with additional batteries, added loads, and the old undersized
wiring things will be different. In general these alternators work or they
don't. Rare for them to get weak although a slipping belt can drastically
reduce performance.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Don Hanson
Sent: Tuesday, January 21, 2014 7:55 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Alternator questions

Inline Vw motor, digifant electronics.  Same alternator as Vanagon, etc.
This alternator is about 4 yrs old now, sourced from Van Cafe. It has been
worked hard keeping 2 batteries charged through extensive prolonged off-grid
camping. I've gone through 3 standard starting batteries, often draining the
auxiliary battery charging electronics, etc.

Today my aux battery was low so I plugged my 12v power source for my lap top
into a power point that's wired to the engine battery.  The laptop's battery
was dead, but I figured the bigger engine battery would have the juice to
charge the computer and still fire up the van. Wrong, the laptop's battery
took most of the charge from the van.  Tried jumping.from the coach battery
but that one was dead, too.  Did a one-man push start and drove around for
half hour.  Starts right up again, but I put my multimeter across the
vehicle main and it reads just 13.2v engine idling with no accessories on.
Pretty low, according to Bentley.  Would that be Reg/brushes ? in that time
span and the use cycle?

Is the test just to get some new brushes and stick em in, then check the
battery input again?

Thanks, Don H.